View Full Version : My New Prototype Digital Interconnect
walpurgis
18-02-2015, 00:27
Just finished making myself a new digital coax lead.
http://i59.tinypic.com/w86l5l.jpg
It uses Van Damme cable. Listening trials start tomorrow. I shall report back. I'm expecting good things. :)
Looks good - a nice neat job. :)
Can you tell us which Van Damme cable it is? I assume it has a 75Ohm impedance. How long is it?
walpurgis
18-02-2015, 16:04
Yes. It is 75 ohm cable. This one is 1 metre long.
I'm expecting good things.
How does it differ from any other cable?
How does it differ from any other cable?
It's green and hand made by Geoff. :lol:
walpurgis
19-02-2015, 10:44
How does it differ from any other cable?
Digital coax cables (like analogue ones) differ in how they allow the system to sound. I have some extremely good cable types available already, but this is a new previously untried one I'm experimenting with.
Looks good - a nice neat job. :)
Can you tell us which Van Damme cable it is? I assume it has a 75Ohm impedance. How long is it?
its made by their Irish devision...O'van damme:eyebrows:
walpurgis
19-02-2015, 11:06
its made by their Irish devision...O'van damme:eyebrows:
I keep a little leprechaun in the shed putting these together.
(he doesn't mind 'cos I don't keep asking him where his pot of gold is :))
I keep a little leprechaun in the shed putting these together.
(he doesn't mind 'cos I don't keep asking him where his pot of gold is :))
And as all specialist audio cable manufacturers know, the best cables are those that have been assembled under the light of a full moon! :D
to be sure to be sure!
thats the end of the jokes folks. my mad hr is over
brian2957
19-02-2015, 11:50
I thought you were like that all the time Grant :lol:
I thought you were like that all the time Grant :lol:
alas many would rightly agree Brian. ..still, better mad than bad:)
walpurgis
19-02-2015, 18:49
alas many would rightly agree Brian. ..still, better mad than bad:)
Recent quote "I've been bad again"! :eyebrows:
http://img1.wikia.nocookie.net/__cb20130909105555/pacificrim/images/0/09/Homer-Simpson-wingnuts-doh.gif
walpurgis
19-02-2015, 23:44
Here's another one of my 'specials'.
http://i57.tinypic.com/o5dc0g.jpg
Just completed, these digital coax interconnects sound very nice indeed. A different type of cable to the first one shown. I've been turning these out for a couple of years. Grant has one (amongst others). Keeping quiet about exactly what it is 'cos I may flog a few.
Here's another one of my 'specials'.
http://i57.tinypic.com/o5dc0g.jpg
Just completed, these digital coax interconnects sound very nice indeed. A different type of cable to the first one shown. I've been turning these out for a couple of years. Grant has one (amongst others). Keeping quiet about exactly what it is 'cos I may flog a few.
Ah, that IS the one I have...its darned good and It will take the shifting:eyebrows:
maxrob200
26-02-2015, 23:07
Just curious...how does it compare to the Belden 1694 which is sold by several companies under different names
walpurgis
26-02-2015, 23:10
Not having used the Belden, I can't say.
maxrob200
26-02-2015, 23:16
There is also discussion in some forums about optimal length for digital co-ax being 1.5m
walpurgis
26-02-2015, 23:36
There is also discussion in some forums about optimal length for digital co-ax being 1.5m
I've never used one longer than 1 metre length. Although I'd have thought that would be down to the ability of the cable in question. What would govern things to 1.5m?
Long signal leads can affect low level analogue signals in some situations, but I'd expect digital information to be far less susceptible to degradation. If a digital signal is not transferred intact it does not transfer at all. Checksums and all that.
What would govern things to 1.5m?
I read a long article on this (linked to on this very site..)
The gist being that cables shorter than 1.5 metre are prone to a kind of 'bounce back' effect where the digital stream flows back to the source corrupting the signal in it's wake.
Obviously the article was way more complicated than this and as exciting as counting mobility scooters in Asda
..found that article ;)
http://www.positive-feedback.com/Issue14/spdif.htm
EXTRACT:
"If the rise-time is 25 nanoseconds and the cable length is 3 feet, then the propagation time is about 6 nanoseconds. Once the transition has arrived at the receiver, the reflection propagates back to the driver (6 nanoseconds) and then the driver reflects this back to the receiver (6 nanoseconds) = 12 nanoseconds. So, as seen at the receiver, 12 nanoseconds after the 25 nanosecond transition started, we have a reflection superimposing on the transition. This is right about the time that the receiver will try to sample the transition, right around 0 volts DC. Not good. Now if the cable had been 1.5 meters, the reflection would have arrived 18 nanoseconds after the 25 nanosecond transition started at the receiver. This is much better because the receiver has likely already sampled the transition by this time."
walpurgis
27-02-2015, 11:30
That may suggest there is an optimum length. However, most digital cables are shorter and seem to work without problems. As I said, digital information has to arrive intact or not at all. All mine are a metre or less and sound very good. Apart from a fairly expensive Townshend example which does not impress me.
That may suggest there is an optimum length. However, most digital cables are shorter and seem to work without problems. As I said, digital information has to arrive intact or not at all. All mine are a metre or less and sound very good. Apart from a fairly expensive Townshend example which does not impress me.
what you doing giving me a short digi cable geoff:steam: get it changed man:lolsign:
walpurgis
27-02-2015, 12:09
what you doing giving me a short digi cable geoff:steam: get it changed man:lolsign:
Sorry about that. It's complete crap I know! :lol:
Sorry about that. It's complete crap I know! :lol:
you will HAVE to make a longer one now...you know it;)
walpurgis
27-02-2015, 12:44
you will HAVE to make a longer one now...you know it;)
If you need a longer one to go between the CD/DIP or DIP/DAC let me know.
As I said, digital information has to arrive intact or not at all.
I'm no expert but what he (and others) seem to be implying is that it's not an 'all or nothing' scenario. Any ambiguity in the data stream can lead to faulty extrapolation in the interpretation at the DAC which may be converted as audible artefacts (like jitter or loss of focus). Occasional ambiguities will go unnoticed but if the interference pattern is consistent and systematic the degradation is more likely. I suppose a lot will also depend on how well designed the DAC is and how it deals with error correction ....
I've never used one longer than 1 metre length. Although I'd have thought that would be down to the ability of the cable in question. What would govern things to 1.5m?
Long signal leads can affect low level analogue signals in some situations, but I'd expect digital information to be far less susceptible to degradation. If a digital signal is not transferred intact it does not transfer at all. Checksums and all that.
What checksums?
... incidentally - I have two 75 ohm coax cables (2m and the other at 1m) and have tried them both on my DVD player to DAC.
Guess which one sounded best :lol:
Marco might be able to tell you the audible difference (if any) between a digital cable 1m long and one that is longer.
The article about pulse transition corruption due to signal mismatch reflection is correct in principle. However it is the level of the mismatch that is important - how close the output impedance of the player and the input impedance of the DAC is to 75ohm. If the mismatch is poor (say < 8db RL) the length of cable used will depend on the sampling rise-time. Conversly if the mismatch is low (> 30dB RL), any cable length will do.
I found it to be correct in practice as well. The impedance mismatch will always be poor as RCA's are used. To think that a digital signal is not transferred intact it's not transferred at all is quite wrong, it's not a case of bits is bits. A better approach is to think of it as a high frequency analogue signal, SPDIF looks not too dissimilar to a FM signal.
...and on another tack; This may just be my issue but I find this thread does not sit too well with me. The OP opens with a post that sets an expectation bias on performance and follows it up later with another about being secretive about the cable used because he may ‘flog a few’ at some point. Anybody can view the VD catalogue on line and I wonder why the need for secrecy, this is off the reel cable not bespoke manufactured stuff….and this is from a Moderator of this board who I take it is not thinking about being a Trade member…as I said it may just be me.
walpurgis
28-02-2015, 00:50
And?
Stratmangler
28-02-2015, 00:53
Yes. It is 75 ohm cable. This one is 1 metre long.
Have you measured it with your DMM?
I only ask, 'cos folk bandy this kind of stuff around ....
You can't measure the characteristic impedance of a cable with a DMM, you have to rely on the manufacturer's specification.
walpurgis
28-02-2015, 10:43
Recently turned out speaker cables.
http://i57.tinypic.com/28t8gw4.jpg
Yes I did show these before elsewhere.
they look pretty sturdy Geoff. a little like my mit stuff
walpurgis
28-02-2015, 10:48
Recently made analogue interconnect pair.
http://i57.tinypic.com/55klu9.jpg
These have been seen elsewhere too.
walpurgis
28-02-2015, 10:49
they look pretty sturdy Geoff. a little like my mit stuff
They're Audioquest Type 6. Not expensive, but very decent sounding.
...and on another tack; This may just be my issue but I find this thread does not sit too well with me. The OP opens with a post that sets an expectation bias on performance and follows it up later with another about being secretive about the cable used because he may ‘flog a few’ at some point. Anybody can view the VD catalogue on line and I wonder why the need for secrecy, this is off the reel cable not bespoke manufactured stuff….and this is from a Moderator of this board who I take it is not thinking about being a Trade member…as I said it may just be me.
I suspect Geoff had his tongue fairly well into his cheek.
walpurgis
28-02-2015, 12:38
I suspect Geoff had his tongue fairly well into his cheek.
He certainly does! :lol:
There are things said on forums that would be unlikely to be spoken face to face.
My apologies to Geoff if I've misread his thread, far too subtle for me.
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